GENERAL DISCUSSION 751 



might be possible to use radiation as a discriminative stimulus. I am not aware 

 that any work like this has been done. One could determine the time required to 

 show such a discrimination; and if a situation were set up where the responding 

 and behavior were measured from moment to moment, it might throw some light 

 on whether conditioned avoidance and the conditioned taste aversion were due to 

 a direct sensory perception of the irradiation, or whether the effect was due to the 

 animal's perceiving the autonomic or other secondary effect resulting from the 

 radiation. I think such an experiment could be set up using differential reinforce- 

 ment of low rad versus a variable ratio, and having the radiation turned on during 

 one of the components, the radiation, therefore, being the only possible way in 

 which the animal could tell what the reinforcement schedule would be. I wonder 

 if Dr. Kimeldorf has done any work along this line, using radiation as a dis- 

 criminative stimulus. If he has not, I would like to know whether he would 

 hazard a guess as to whether the aversions and avoidances he found are due to 

 direct sensory perception of the radiation source or due to the autonomic or other 

 effects of the radiation. 



Donald J. Kimeldorf (U. S. Naval Radiological Defense Laboratory, San 

 Francisco, California): Dr. Falk has been reading our secret protocols. We are in 

 the process of attempting to use radiation as a conditioned stimulus, rather than 

 as the unconditioned stimulus. Other than what we have said in our formalized 

 presentation, which was carefully considered with regard to perception and moti- 

 vation of radiation, I hesitate to make any judgments yet. What appears to be 

 indications and perhaps proof of late effects of alteration in behavior has been of 

 interest to me in another regard. We know that radiation exposure does shorten 

 life span. This has been shown in several species. We do not know if this is a 

 simulation of or stimulation of the normal aging processes. It may be that the 

 same system that responds to radiation is the one that reacts to radiation processes 

 which show up in aging. Those people who find these late effects hold their 

 controls for a longer time to determine whether there is any relationship between 

 the alteration behavior which occurs early in the irradiated animal. It might not 

 occur in the same time sequence with regard to life span. If someone has not 

 tested controls at a later date, it might be valuable to do so. 



Donald B. Lindsley (University of California, Los Angeles, California): It 

 seems to me that during the past 3 days we have heard some very interesting papers 

 which have brought definite questions before us. One relates to the dosage; one 

 relates to a question that Dr. Furchtgott brought out. We have heard that in those 

 cases where doses were approaching sublethal doses, or even considerably less, 

 there often was a decrement in performance or a depressant effect. Where the 

 dosage was considerably less, say under 200 r or 75 r, we noticed in several in- 

 stances, in Dr. Harlow's survey and several others, that there was for these lower 

 dosages a definite sensitizing influence with increasing performance on the various 

 tests. Above that, the decrement began to set in. In the papers from other sessions 

 of the symposium, we noticed something of the same sort where a peripheral 

 nerve or receptor system was radiated. There was indication on Gaffey's paper, 

 Noell's, Lipetz's, and others, that there was at first an increased responsiveness 

 even of peripheral structures. In C. A. Tobias' paper, pointing out the nature of 



